How would you know what would and wouldn't have made a difference? You don't, you have no idea. You're just making things up to justify your position that he wasn't NHL material. And you know what, he might not be; he might not be able to play in the NHL. I don't know what would have happened if the Flyers gave him 80 games in the NHL.
But 35 games, over two seasons, with garbage linemates, isn't going to give you an adequate sample size to make that determination. That's the point. The Flyers didn't give him a real opportunity to develop confidence and to learn how to play at the NHL level. And as a result, they may be missing out on a middle-6 center. This is a prime example of a failure in player development. It doesn't matter if it turned out he couldn't play in the NHL. It shows an extremely flawed process - they do not put the younger marginal players in positions to succeed.
In terms of refining his game, that is player development. That's how you develop players. By age 20-22, in general players don't get markedly better at hockey skills. In other words, by their early 20's players either have sufficient skill or they don't. What they don't have is experience at the NHL level. It's not like player X gets better at poke-checking. It's that player X gets a better understanding for when to poke check, or when to step-up, or when to pass, etc. You can only do that by playing in the NHL.